The importance of lysosomal enzymes is underscored by the existence of about 30 human genetic disorders, in which deficiency of an enzyme leads to lysosomal storage of its undegraded substrate, to cellular pathology and to clinical disease. The deficiency of specific lysosomal enzymes, resulting in accumulation and storage of undegraded substrates, may be secondary manifestation of some other underlying defect such as over-or underglycosylation of the enzyme in question. To date, there have been no detailed structural studies on the carbohydrate moieties of any of the lysosomal enzymes. The goal of this proposed research is to investigate the structural features of the oligosaccharide side chains of purified lysosomal acid alpha-glucosidase from human liver, with respect to: 1) the nature of the covalent linkage to protein; 2) size and charge heterogeneity; 3) sugar composition; 4) sequence; and, 5) nature of linkages of individual sugar constituents. These goals can be achieved using existing methodology. Primarily, these methods include: 1) borohydride reduction; 2) paper radiochromatographic scanning; 5) high-voltage paper electrophoresis; and, 6) gel filtration. This work sets the stage for future work entailing comparison of structural features of the various isoelectric focusing forms. This includes evaluation of the sites of glycosylation, the degree of covalent modification, such as phosphorylation, and oligosaccharide side chain processing.